我国非粮燃料乙醇的原料资源量分析

目前世界燃料乙醇的生产原料约60%为甘蔗或甜菜等糖质原料、33%为玉米或小麦等淀粉质原料,而纤维质原料正日益受到重视。我国可用于生产燃料乙醇的非粮淀粉质原料主要有甘薯、木薯、蕉藕、葛根等。其中蕉藕目前尚未形成产业化生产;葛根原料价格高,不宜作为乙醇原料;甘薯归属粮食范畴;只有木薯是最适宜制燃料乙醇的非粮淀粉质原料。纤维质原料主要包括农作物秸秆、农林废弃物、木屑等,其中农作物秸秆是我国产量最大的非粮燃料乙醇原料。秸秆资源密度考虑,利用区域应主要集中在河南、山东、江苏等地,保守估计这3个省的秸秆量可供生产1117×104t乙醇。目前制约纤维质原料制乙醇的关键瓶颈之一是原料的收集、运输及供应保障,若没有国家大的政策扶持和资金补贴,纤维质原料因缺乏经济可行性而尚不具备工业化生产乙醇的条件。糖质原料主要有甘蔗、甜菜、甜高粱茎秆和菊芋。由于菊芋菊粉附加值高,不宜作乙醇原料;甘蔗、甜菜主要用于糖业,不会作为乙醇原料;从单位土地面积乙醇产量和原料成本、农民种植收益综合来看,甜高粱茎秆是适宜生产燃料乙醇的糖质原料。需要寻求产业化种植模式来落实资源总量,提高资源保障度;另一方面要进一步研究低成本、安全保质的茎秆储藏技术。     

Progress in bioethanol processing

Production of ethanol (bioethanol) from biomass is one way to reduce both consumption of crude oil and environmental pollution. Bioethanol is appropriate for the mixed fuel in the gasoline engine because of its high octane number, and its low cetane number and high heat of vaporization impede self-ignition in the diesel engine. So, ignition improver, glow-plug, surface ignition, and pilot injection are applied to promote self-ignition by using diesel-bioethanol-blended fuel. Disadvantages of bioethanol include its lower energy density than gasoline, its corrosiveness, low flame luminosity, lower vapor pressure (making cold starts difficult), miscibility with water, and toxicity to ecosystems. Bioethanol can be produced from cellulosic feedstocks. One major problem with bioethanol production is the availability of raw materials for the production. The availability of feedstocks for bioethanol can vary considerably from season to season and depends on geographic locations. Lignocellulosic biomass is the most promising feedstock considering its great availability and low cost, but the large-scale commercial production of fuel bioethanol from lignocellulosic materials has still not been implemented. Conversion technologies for producing bioethanol from cellulosic biomass resources such as forest materials, agricultural residues and urban wastes are under development and have not yet been demonstrated commercially. For designing fuel bioethanol production processes, assessment of utilization of different feedstocks (i.e. sucrose containing, starchy materials, lignocellulosic biomass) is required considering the big share of raw materials in bioethanol costs. In this work a review of the biological and thermochemical methods that could be used to produce bioethanol is made and an analysis of its global production trends is carried out.     

Developments in the scale-up of the vortex-pyrolysis system

Fundamental and applied research and engineering development over the past 13 years has demonstrated that continuous reactors could be used with very fast heating rates and short residence times to produce high yields of liquids from biomass. The National Renewable Energy Laboratory developed the ablative pyrolysis system and Interchem Environmental is commercializing this technology. Interchem designed and built a first generation, 32.7 tonnes (36 tons) per day, prototype ablative pyrolysis system in Missouri. The system was operated for 15 months with varying degrees of success. A second generation plant was designed based on the operating data collected from the first plant and on NREL's design for the vortex reactor. This facility is currently being built in Kansas City, KS. This paper discusses the design and operation of the first generation prototype facility and the design of the second generation system. The second plant is designed to produce 70% oil, 15% char and 15% non-condensible gases from the incoming wood. The oil will be sold as boiler fuel, the char sold as a feedstock to charcoal briquette manufacturers and the gases burned to provide process heat. Upon successful commercialization of this process, agricultural and forest residues can be converted into valuable products. In addition, the process offers a mechanism to use biomass as a feedstock for chemical production rather than relying on petroleum feedstocks.     

Economic sustainability for wood pellets production – A comparative study between Finland,Germany, Norway,Sweden and the US

The consumption of wood pellets grew rapidly during the last decade. In this paper we compare the development of the production factors for wood pellet markets in Finland, Germany, Sweden, Norway and the US; we analyze how domestic market prices for pellet production factors as well as domestic market prices for pellets vary among the countries. The analyses are based on two model plants. The first represents common technologies for small scale pellet production based on dry residues from sawnwood production, while the second represents large scale production based on a blend of dry and wet materials. The results show how differences in costs of feedstock, energy and labor affect the profitability of pellet production and hence the development of pellet production in the analyzed countries. Pellet producers in the US have lower feedstock costs than producers in the analyzed European countries. The economic sustainability for European pellet producers depends to a large extent on their domestic markets as internationally traded pellets are priced lower than their production costs. Future pellet production will, to a greater extent, be based on wet feedstock such as roundwood and wet sawdust. These feedstocks are also demanded by wood-based industries (pulp and paper, particle- and fiber-board) as well as for traditional fuelwood. The transition from smaller pellet plants using dry feedstock to larger plants using wet feedstock in future pellet production, can be expected to follow comparative advantages regarding feedstock and energy costs, but also with respect to economies of scale.     

Strategies for selection of thermo-chemical processes for the valorisation of biomass

Research on biomass conversion has been gaining a lot of interest as biomass is renewable and sustainable in nature. Products from biomass can be obtained by different methods amongst which thermo-chemical route has a very high potential. Biomass is generally available in a localised manner in varying quantities and qualities throughout the year and hence, region specific technologies have to be developed considering the end user requirement. Pyrolysis is a very versatile technique with the above considerations. The process parameters can be tweaked to necessity to produce more bio-oil or bio-char. Thermogravimetric analysis is essential for understanding the decomposition behaviour of the feedstock before the lab scale pyrolysis is carried out. Pyrolysis using several regional feedstocks has been carried out under nitrogen and hydrogen atmosphere and different biomass feedstocks were also liquefied using sub/supercritical solvents. This review aims to provide a comparison of the results obtained using various processes. This helps in the decentralised processing of biomass (dry biomass using pyrolysis and wet biomass by hydrothermal liquefaction) to produce bio-crude which can be upgraded to produce fuels/chemicals/petrochemical feedstocks in an environmental friendly manner.     

Optimizing the operating conditions for hydrogen-rich syngas production in a plasma co-gasification process of municipal solid waste and coal using Aspen Plus

The plasma gasification process is one of the newest and most innovative approaches to meet the needs of waste management but requires assessment and research on operational conditions prior to installation. In this work, a model based on Gibbs free energy minimization was developed and implemented in Aspen Plus®. A combination of municipal solid waste (MSW) and coal has been used as feedstocks. The model's performance was compared with the results of the literature and found to be in good agreement. The effect of various parameters such as temperature, equivalence ratio, MSW/coal blending ratio, and steam-to-feedstock ratio on the composition of syngas and hydrogen production were assessed. Very interesting results were obtained concerning the mixture of the feedstocks that maximize the hydrogen production besides that using steam as a gasifying agent allows higher hydrogen production than using air. When using high amounts of coal in the feedstock mixture, low steam ratios are preferred. When using high amounts of MSW in the feedstock mixture high steam ratios are preferred. The use of pure oxygen as the gasifying agent increases the hydrogen percentage but requires an air separation unit to be included in the process. The results obtained in this study are particularly relevant for countries with coal reserves.     

Approbation of an innovative method of pretreatment of dark fermentation feedstocks

According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen.     

Environmental sustainability assessment of bio-ethanol production in Thailand

Bio-ethanol is playing an important role in renewable energy for transport according to Thai government policy. This study aims to evaluate the energy efficiency and renewability of bio-ethanol system and identify the current significant environmental risks and availability of feedstocks in Thailand. Four of the seven existing ethanol plants contributing 53% of the total ethanol fuel production in Thailand have been assessed by the net energy balance method and Life Cycle Assessment (LCA). A renewability and net energy ratio portfolio has been used to indicate whether existing bio-ethanol production systems have net energy gain and could help reduce dependency on fossil energy. In addition, LCA has been conducted to identify and evaluate the environmental hotspots of ‘cradle to gate’ bio-ethanol production. The results show that there are significant differences of energy and environmental performance among the four existing production systems even for the same feedstock. The differences are dependent on many factors such as farming practices, feedstock transportion, fuel used in ethanol plants, operation practices and technology of ethanol conversion and waste management practices. Recommendations for improving the overall energy and environmental performance of the bio-ethanol system are suggested in order to direct the bio-ethanol industry in Thailand towards environmental sustainability.     

Comparing biological and thermochemical processing of sugarcane bagasse: An energy balance perspective

The technical performance of lignocellulosic enzymatic hydrolysis and fermentation versus pyrolysis processes for sugarcane bagasse was evaluated, based on currently available technology. Process models were developed for bioethanol production from sugarcane bagasse using three different pretreatment methods, i.e. dilute acid, liquid hot water and steam explosion, at various solid concentrations. Two pyrolysis processes, namely fast pyrolysis and vacuum pyrolysis, were considered as alternatives to biological processing for the production of biofuels from sugarcane bagasse. For bioethanol production, a minimum of 30% solids in the pretreatment reactor was required to render the process energy self-sufficient, which led to a total process energy demand equivalent to roughly 40% of the feedstock higher heating value. Both vacuum pyrolysis and fast pyrolysis could be operated as energy self-sufficient if 45% of the produced char from fast pyrolysis is used to fuel the process. No char energy is required to fuel the vacuum pyrolysis process due to lower process energy demands (17% compared to 28% of the feedstock higher heating value). The process models indicated that effective process heat integration can result in a 10-15% increase in all process energy efficiencies. Process thermal efficiencies between 52 and 56% were obtained for bioethanol production at pretreatment solids at 30% and 50%, respectively, while the efficiencies were 70% for both pyrolysis processes. The liquid fuel energy efficiency of the best bioethanol process is 41%, while that of crude bio-oil production before upgrading is 67% and 56% via fast and vacuum pyrolysis, respectively. Efficiencies for pyrolysis processes are expected to decrease by up to 15% should upgrade to a transportation fuel of equivalent quality to bioethanol be taken into consideration.     

Co-gasification of wastewater sludge and different feedstock: Feasibility study

Gasification experiments were performed for several feedstocks alone (wastewater sludge, waste wood, reeds, olive pomace, solid recovered fuel, paper labels and plastic labels) using a fixed bed reactor operating in semi-batch conditions. In order to combine them in an optimal gasifying blend, the gasification behavior of each feedstock was compared with that of wastewater sludge through the following criteria: the raw feedstock proximate and ultimate composition, the solid conversion, the gas heating value, the pollutants release and the ashes melting. Operated alone, the conversion rate of the feedstocks after 58 min of solid residence time was over 77% of initial mass. The Syngas low heating value produced at 1123 K was in the range of 9.0 to 11.9 MJ m⁻³. The major concerns regarding the wastewater sludge were the pollutants precursors' release (NH₃, COS…) and the ash slagging and fouling. The calculated slagging and fouling indexes were high also for olive pomace and for waste wood. Finally, among the possible blends studied the paper labels and plastic labels can be co-gasified with secondary and digested wastewater sludge without any restriction, reeds and solid recovered fuel can be blinded with secondary wastewater sludge without any restriction, a specific attention have to be taken to fouling when they are blended with digested wastewater sludge. The blend based on waste wood and olives pomace should be avoided for instance due to their ash slagging and fouling tendency.     

Optimizing feedstock selection for biofuel production in Hawaii: CuO oxidative lignin products in C4 grasses

Global interest in renewable fuels is rapidly growing with particular emphasis on local energy growth and creating new energy feedstocks, specifically liquid fuel sources. However, the interactive effect of plant species/variety and growth environment on plant structural components, which may influence conversion efficiency and thus play an important role in optimizing the production of biofuels, is not fully understood. In this study cupric oxide (CuO) extractable lignin, which extracts and quantifies lignin-derived monomers, was determined for 25 cultivated and naturalized tropical perennial C₄ grass varieties of napiergrass and Guinea grass that were under assessment for suitability as feedstocks for liquid fuel generation. Principal component analysis of CuO extractable lignin-derived monomers showed differences in composition between napiergrass and Guinea grass, as well as environmental differences within many, but not all napiergrass varieties. Among the samples tested, the greatest differences in lignin composition occurred specifically in vanillyl lignin structures. A wide range (1–2.5) in the ratio of cinnamyl to vanillyl structures (C/V), which often relates to enzymatic degradability in natural systems, was also found. It is expected that the observed CuO lignin differences representing the structure and bonding of lignin will relate to ease of chemical and enzymatic conversion and the effectiveness of pretreatment and conversion in biofuel application. We hypothesize that the C/V ratio of feedstock will positively relate to conversion efficiency and if supported, then compositional lignin metrics such as the C/V ratio could be a predictor to select for more easily degradable biomass for biofuel production.     

Bioenergy in Australia: An improved approach for estimating spatial availability of biomass resources in the agricultural production zones

Bioenergy production from crops and agricultural residues has a greenhouse gas mitigation potential. However, there is considerable debate about the size of this potential. This is partly due to difficulties in estimating the feedstock resource base accurately and with good spatial resolution. Here we provide two techniques for spatially estimating crop-based bioenergy feedstocks in Australia using regional agricultural statistics and national land use maps. The approach accommodates temporal variability by estimating ranges of feedstock availability and the shifting nature of zones of the highest spatial concentration of feedstocks. The techniques are applicable to biomass production from forestry, agricultural residues or oilseeds, all of which have been proposed as biofuel feedstocks.     

Integration of algae-based biofuel production with an oil refinery: Energy and carbon footprint assessment

Biofuel production from algae feedstock has become a topic of interest in the recent decades since algae biomass cultivation is feasible in aquaculture and does therefore not compete with use of arable land. In the present work, hydrothermal liquefaction of both microalgae and macroalgae is evaluated for biofuel production and compared with transesterifying lipids extracted from microalgae as a benchmark process. The focus of the evaluation is on both the energy and carbon footprint performance of the processes. In addition, integration of the processes with an oil refinery has been assessed with regard to heat and material integration. It is shown that there are several potential benefits of co-locating an algae-based biorefinery at an oil refinery site and that the use of macroalgae as feedstock is more beneficial than the use of microalgae from a system energy performance perspective. Macroalgae-based hydrothermal liquefaction achieves the highest system energy efficiency of 38.6%, but has the lowest yield of liquid fuel (22.5 MJ per 100 MJ_algae) with a substantial amount of solid biochar produced (28.0 MJ per 100 MJ_algae). Microalgae-based hydrothermal liquefaction achieves the highest liquid biofuel yield (54.1 MJ per 100 MJ_algae), achieving a system efficiency of 30.6%. Macro-algae-based hydrothermal liquefaction achieves the highest CO₂ reduction potential, leading to savings of 24.5 resp 92 kt CO_2eq/year for the two future energy market scenarios considered, assuming a constant feedstock supply rate of 100 MW algae, generating 184.5, 177.1 and 229.6 GWh_biochar/year, respectively. Heat integration with the oil refinery is only possible to a limited extent for the hydrothermal liquefaction process routes, whereas the lipid extraction process can benefit to a larger extent from heat integration due to the lower temperature level of the process heat demand.     

Performance of diesel engine using biodiesel obtained from mixed feedstocks

Availability of identified tree species bearing non-edible oil has a region specific production characteristics and availability of sufficient amount at a given place is always uncertain. Moreover, the any prospective biodiesel production and utilization programe would need to consider more and one feedstock to meet the target. There could be another reason to investigate feasibility of mixed feedstocks considering strength and weakness of biodiesel fuel properties specific to feedstocks. Considering the above the present investigation is carried out to study the fuel characteristics of biodiesel obtain from mixed feedstocks of three species of oil feedstocks namely polonga, koroch and jatropha. An attempt has been made in this paper to give an overview of the application of mixed biodiesel in CI Engine. Properties of biodiesel obtained from mixed feedstocks (BOMF) satisfy different biodiesel standards. Performance of BOMF fueled engine gives better result than the individual biodiesels.     

A two-step approach to the hydrothermal gasification of carbohydrate-rich wastes: Process design and economic evaluation

A two-step approach to hydrothermal gasification of carbohydrate-rich wastes and wastewaters is a promising route for H₂ production and simultaneously as a water clean-up technology. Experimental data and kinetic models are used to further develop the process for industrial scale. In this work, a preliminary process design is conducted in order to assess the market potential of the two-step process. For stabilisation, two cases are considered: the use of excess vs. stoichiometric H₂, and for gasification, the utilisation of sequential reactors for gasification housing Pt and Ru catalysts is compared to a single reactor with Pt alone. A total of four options are conceptually designed and economically evaluated. Using state-of-the-art insights and process techniques and the current market scenario, a minimum H₂ selling price of 3.4 $ kg⁻¹ was obtained.A sensitivity study showed that the feedstock price, concentration and quantity, played a crucial role in the selling price of H₂. These variables are all correlated and are dependent on the industry from where the feedstock is obtained. Industrial wastewater streams rich in carbohydrate residues and associated with gate fees were found to be promising feedstock for the process.Further advancement in the areas of catalyst development (hydrothermal stability, affordability) as well as increased H₂ yields are necessary in order to improve the economics of this process on industrial scale.     

Biodiesel from low cost feedstocks: The effects of process parameters on the biodiesel yield

Biofuel (e.g. biodiesel) has attracted increasing attention worldwide as blending component or direct replacement for fossil fuel in fuel energized engines. The substitution of petroleum-based diesel with biodiesel has already attained commercial value in many of the developed countries around the world. However, the use of biodiesel has not expanded in developing countries mostly due to the high production cost which is associated with the expensive high-quality virgin oil feedstocks. This research focuses on producing of biodiesel from low cost feedstocks such as used cooking oil (UCO) and animal fat (AF) via alkaline catalyzed transesterification process investigating the effects of process parameters, for example (i) molar ratio of feedstock to methanol (ii) catalyst concentration (iii) reaction temperature and (iv) reaction period on the biodiesel yield. The biodiesel was successfully produced via transesterification process from low cost feedstocks. It was also observed that the process parameters directly influenced the biodiesel yield. The optimum parameters for maximum biodiesel yields were found to be methanol/oil molar ratio of 6:1, catalyst concentration of 1.25 wt% of oil, reaction temperature of 65 °C, reaction period of 2 h and stirring speed of 150 rpm. The maximum biodiesel yields at the optimum conditions were 87.4%, 89% and 88.3% for beef fat, chicken fat and UCO, respectively. The results demonstrate high potential of producing economically viable biodiesel from low cost feedstocks with proper optimization of the process parameters.     

Biodiesel production from renewable feedstocks: Status and opportunities

The increased demand for energy, climate change, and energy security concerns has driven the research interest for the development of alternative fuel from plant origin. Biodiesel derived from plant oils, which include edible and non-edible oil have gained interest for the last two decades as alternative for diesel around the world. Among these plant origin oils more than 95% of biodiesel production feedstocks come from edible oils, because they are readily available in many regions. The major advantage of these feedstocks is the properties of biodiesel produced from them are suitable to be used as diesel fuel substitute. But the consequence is the increase demand of the feedstock for food as well as fuel. A sustainable alternative fuel should be derived from renewable non-food biomass sources. The main objective of this review is to give an overview on the synthesis of biodiesel through esterification and transesterification using non-edible oil resources which are available in India, and available processes for synthesis of biodiesel (acid-, base-catalyzed transesterification reactions (homogeneous and heterogeneous), their importance, and which is the commercial process also discussed here.     

Pretreatment methods to obtain pumpable high solid loading wood–water slurries for continuous hydrothermal liquefaction systems

Feedstock pretreatment is a prerequisite step for continuous processing of lignocellulosic biomass through HTL, in order to facilitate the pumpability of biomass aqueous slurries. Until now, HTL feedstock pumpability could only be achieved at solid mass content below 15%. In this work, two pretreatment methods to obtain wood-based slurries with more than 20% solid mass content, for continuous processing in HTL systems, are proposed. The effect of biomass particle size and pretreatment method on the feedstock pumpability is analyzed. The experimental results show that pumpable wood-based slurries containing 20% solids can be prepared using recycle HTL biocrude as carrier fluid, if particles smaller than 0.125 mm are used. The recycle biocrude concentration used for slurry make-up is strongly affected by the sawdust size distribution. A second pretreatment option is feedstock thermal treatment with alkalis. This method is less sensitive to particle size or wood type. 1 mm particles of either softwood or hardwood could be converted into pumpable liquid feedstock by thermal treatment with NaOH at 180 °C. Wood-water-biocrude slurries viscosity is reduced from 100 to 1000 Pa s to about 1 Pa s, when thermal treatment is applied.     

Industrial scale production of hydrogen from natural gas,naphtha and coal

This paper reviews the three major routes for the production of hydrogen from fossil fuels.Today there is considerable interest in the production of hydrogen via the gasification of coal. Existing processes and developments are listed.The partial oxidation processes which utilize feedstocks ranging from light hydrocarbons to heavy fuel oil are attractive due to feedstock flexibility.Hydrogen production based on the steam reforming of light hydrocarbons has become the most widely used process as a result of, in general, better economics.     

Competition for the biomass resource: Greenhouse impacts and implications for renewable energy incentive schemes

In Australia, the Mandatory Renewable Energy Target (MRET) scheme, which targets a 9.5 TWh per annum increase in renewable electricity generation by 2010, is stimulating interest in bioenergy. Development of bioenergy projects may cause competition for biomass resources. For example, sawmill residues are an attractive feedstock for bioenergy, but are also utilised for particleboard manufacture. This study compares the greenhouse gas (GHG) mitigation impacts of alternative scenarios where sawmill residues are used either for generation of electricity or for manufacture of particleboard. The study considers a theoretical particleboard plant processing 100 kt feedstock of dry sawmill residues per annum. If the sawmill residues are used instead for bioenergy, and the particleboard plant utilises fresh plantation biomass, 205 kt CO₂eq emissions are displaced. However, GHG emissions for particleboard manufacture increase by about 38 kt CO₂eq, equivalent to 19% of the fossil fuel emissions displaced, due to the higher fossil fuel requirements to harvest, transport, chip and dry the green biomass. Also, plantation carbon stock declines by 147 kt CO₂eq per year until a new equilibrium is reached after 30 years. This result is influenced particularly by the fossil fuel displaced, the relative efficiency of the fossil fuel and bioenergy plants, the moisture content of the sawmill residues, and the efficiency of the dryer in the particleboard plant.Under MRET, calculation of Renewable Energy Certificates is based solely on the quantity of power generated. This study illustrates that indirect consequences can reduce the GHG mitigation benefits of a bioenergy project. Increased emissions off-site, and loss of forest carbon stock, should be considered in calculating the net GHG mitigation benefit, and this should determine the credit earned by a bioenergy project.